U.S. patent number 7,491,664 [Application Number 11/388,094] was granted by the patent office on 2009-02-17 for wet friction material.
This patent grant is currently assigned to NSK-Warner Kabushiki Kaisha. Invention is credited to Sousuke Kawai, Masahiro Mori, Hirokazu Yagi.
United States Patent |
7,491,664 |
Mori , et al. |
February 17, 2009 |
**Please see images for:
( Certificate of Correction ) ** |
Wet friction material
Abstract
The invention provides a wet friction material having high
friction coefficient, excellent compression fatigue property and
positive gradient of a .mu.-V property. The wet friction material
contains a paper base material and a binder, in which the binder
contains a cured material of a liquid resin composition obtained by
mixing a hydrolyzed solution of a silane coupling agent represented
by the following formula (1) and a resol-type phenol resin, and a
weight ratio (S/R) between respective non-volatile components of
the hydrolyzed solution (S) of the silane coupling agent and the
resol-type phenol resin (R) is in the range of from 80/20 to 20/80:
(X)(R.sup.1).sub.nSi(OR.sup.2).sub.3-n (1), in which X represents
an alkylamino group having a primary amine at a terminal; R.sup.1
and R.sup.2 each independently represent an alkyl group having from
1 to 3 carbon atoms; and n represents an integer of 0 or 1.
Inventors: |
Mori; Masahiro (Shizuoka,
JP), Yagi; Hirokazu (Shizuoka, JP), Kawai;
Sousuke (Shizuoka, JP) |
Assignee: |
NSK-Warner Kabushiki Kaisha
(Tokyo, JP)
|
Family
ID: |
37071435 |
Appl.
No.: |
11/388,094 |
Filed: |
March 24, 2006 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20060223907 A1 |
Oct 5, 2006 |
|
Current U.S.
Class: |
442/157; 428/391;
442/149 |
Current CPC
Class: |
C08G
8/28 (20130101); C08L 61/06 (20130101); F16D
69/026 (20130101); F16D 2200/0095 (20130101); Y10T
442/2803 (20150401); Y10T 442/2738 (20150401); Y10T
428/2962 (20150115) |
Current International
Class: |
B32B
5/02 (20060101); B32B 9/00 (20060101) |
Field of
Search: |
;442/157,149 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Salvatore; Lynda
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A wet friction material, comprising: a paper base material; and
a binder, wherein the binder comprises a cured material of a liquid
resin composition obtained by mixing: a hydrolyzed solution of a
silane coupling agent represented by the following formula (1); and
a resol-type phenol resin, wherein a weight ratio (S/R) between
respective non-volatile components of the hydrolyzed solution (S)
of the silane coupling agent and the resol-type phenol resin (R) is
in a range of from 80/20 to 20/80:
(X)(R.sup.1).sub.nSi(OR.sup.2).sub.3-n (1), wherein X represents an
alkylamino group having a primary amine at a terminal; R.sup.1 and
R.sup.2 each represents an alkyl group having from 1 to 3 carbon
atoms; and n represents an integer of 0 or 1; wherein the wet
friction material has a positive gradient in .mu.-V characteristic
property.
2. The wet friction material according to claim 1, wherein the
hydrolyzed solution of the silane coupling agent contains water in
an amount not smaller than the amount permitting hydrolysis of half
numbers of hydrolyzable groups contained in the silane coupling
agent, but not larger than three times as much as the amount
permitting hydrolysis of all the number of hydrolyzable groups
contained in the silane coupling agent.
3. The wet friction material according to claim 1, wherein the
resol-type phenol resin is a resin which has a number average
molecular weight of from 150 to 400 and is obtained by blending any
one of phenols (P) and any one of aldehydes (A) at a molar ratio
(A/P) of from 0.8 to 1.4.
Description
The present invention claims foreign priority to Japanese patent
application No. P.2005-108620, filed on Apr. 5, 2005, the contents
of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wet friction material used in a
friction engaging device such as a clutch or a brake employed
within oil in an automatic transmission of, for example, a
vehicle.
2. Related Background Art
A wet friction material has been used in an automatic transmission
of an automatic vehicle and the like. The automatic transmission of
the automatic vehicle involves a multi-plate clutch in which a
plurality of friction plates each formed by sticking wet friction
materials to surfaces of a metallic substrate (core plate) and a
plurality of separator plates as friction counterpart materials
each formed by a single plate such as a metallic plate are
alternately arranged and is designed so that a driving force is
transmitted by abutting these plates against each other or
interrupting by releasing these plates from each other within ATF
(automatic transmission fluid) used as a lubricating oil.
As a wet friction material used in the oil in this way, a wet
friction material of paper type called as "paper friction material"
is generally used. This wet friction material is generally formed
by paper-making fiber base materials such as natural pulp fibers,
organic synthetic fibers or inorganic fibers with filler such as
diatom earth or a cashew resin and a friction regulator in a wet
manner and, then, by impregnating a binder containing a
thermosetting resin and, subsequently, by curing with heat. As a
resin binder used on this occasion, a phenol resin having excellent
heat resistance, high mechanical strength and a good compression
fatigue property has conventionally been mainly used.
By the way, in a recent industrial field regarding automobiles,
light weight and high efficiency of various parts have been sought
in order to save energy and to achieve light weight. On the other
hand, there is a tendency for seeking high rotation and high output
of an automobile engine. Also in an automatic transmission, in
order to cope with the compactness and light weight of the friction
engaging device and the high rotation and high output of the
automobile engine, regarding the wet friction material, enhancement
of the friction coefficient and further improvements in
heat-resistance and endurance have been sought.
In order to resolve these problems, a technique for compounding
high hard filler such as alumina to the paper base material has
been investigated. However, in this technique, although the
friction coefficient is great in an initial engaging condition,
since an attacking force against the friction counterpart material
is strong, as the usage of the friction material is advanced, the
friction coefficient is gradually decreased. Thus, this technique
is not satisfactory. Further, in the past, resins other than the
phenol resin used as the binder, for example, a silicone resin has
also been investigated. The silicone resin has excellent heat
resistance and endurance based on siloxane bonding of main
structure and does not generate a burned area or peeling-off on a
friction material under a high temperature/high load condition and
has excellent long term stability of friction coefficient. Further,
since the silicone resin is soft, a contact area thereof with the
friction counter material at the time of abutting is increased and,
then, the friction coefficient is increased; however, a compression
fatigue property thereof is bad and a displacement amount of an
entire thickness of the friction material becomes great and a
problem of a long-term stability of friction property remains
unsolved. Thus, a satisfactory friction material could not be
obtained. Further, a .mu.-V (friction coefficient versus velocity)
property may have negative gradient, with the result that, when the
friction material is used in a clutch, a transmission shock may
occur.
That is to say, regarding the wet friction material, there is a
need for seeking further improvement in three factors, that is, the
high friction coefficient, the excellent compression fatigue
property and the positive gradient of .mu.-V property.
Aiming for solving these problems, for example, in Japanese Patent
Unexamined Publication No. JP-A-2002-363542, a resin composition
for wet friction material to be obtained by mixing a resol-type
phenol resin and a hydrolyzed solution of alkoxysilane or a lower
condensate thereof is disclosed. Compared with an ordinary phenol
resin, the friction coefficient or heat resistance has been
improved. However, the compression fatigue property, particularly,
the displacement amount of the entire thickness of the friction
material under a high pressure becomes great, compared with the
ordinary phenol resin. Thus, it can not be said that the resin
composition is satisfactory.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a wet
friction material which has a high friction coefficient, an
excellent compression fatigue property and a positive gradient of a
.mu.-V property.
In order to solve the aforementioned problems, the present
inventors have focused attention on the fact that the silane
coupling agent is widely used for improving performance of a
composite material containing an organic polymer and an inorganic
and/or metal material and intensively exerted studies thereon. The
silane coupling agent is represented by the general formula
Z-SiY.sub.3 in which Z represents a reactive organic functional
group illustrated by an amino group, an epoxy group, a vinyl group,
a methacryl group or a mercapto group; and Y represents a
hydrolyzable group illustrated by an alkoxy group. An action
mechanism of the silane coupling agent is described below. The
hydrolyzable group Y, for example, an alkoxy group, reacts with
water to produce a silanol group which is, then, bonded to a
hydroxy group in a surface of the inorganic material. On the other
hand, the reactive organic functional group Z, for example, an
amino group, reacts with the organic polymer such that the two
groups are chemically bonded to each other. That is, the silane
coupling agent acts as an intermediary between the inorganic
material and the organic material, to thereby effectuate
enhancement of physical strength, enhancement of the affinity of
the inorganic material to the organic resin, suppression of
reduction of physical strength under the condition of high
temperature and high humidity, and so on. By utilizing such
characteristics of the silane coupling agent as described above,
the present inventors have exerted intensive studies aiming for
development of a binder useful for the paper base material which is
generally formed by organic materials such as natural pulp fibers
or organic synthetic fibers and inorganic materials such as diatom
earth and, as a result, have found that it is extremely effective
in solving these problems to use a binder in which a hydrolyzed
solution of a specified silane coupling agent and a resol-type
phenol resin, to thereby accomplish the present invention.
According to a first aspect of the present invention, there is
provided a wet friction material, comprising: a paper base
material; and a binder, wherein the binder comprises a cured
material of a liquid resin composition obtained by mixing: a
hydrolyzed solution of a silane coupling agent represented by the
following formula (1); and a resol-type phenol resin, wherein a
weight ratio (S/R) between respective non-volatile components of
the hydrolyzed solution (S) of the silane coupling agent and the
resol-type phenol resin (R) is in a range of from 80/20 to 20/80:
(X)(R.sup.1).sub.nSi(OR.sup.2).sub.3-n (1), wherein X represents an
alkylamino group having a primary amine at a terminal; R.sup.1 and
R.sup.2 each represents an alkyl group having from 1 to 3 carbon
atoms; and n represents an integer of 0 or 1.
According to a second aspect of the present invention, as set forth
in the first aspect of the present invention, it is preferable that
the hydrolyzed solution of the silane coupling agent contains water
with an amount not smaller than the amount permitting hydrolyzing
for half numbers of hydrolyzable groups contained in the silane
coupling agent but not larger than three times as much as the
amount permitting hydrolyzing for all the number of hydrolyzable
groups contained in the silane coupling agent.
According to a second aspect of the present invention, as set forth
in the first aspect of the present invention, it is preferable that
the resol-type phenol resin is a resin which has a number average
molecular weight of from 150 to 400 and is obtained by blending any
one of phenols (P) and any one of aldehydes (A) at a molar ratio
(A/P) of from 0.8 to 1.4.
According to the invention as set forth in the first aspect of the
present invention, in the wet friction material containing the
paper base material and the binder, since the binder is allowed to
be a cured product of a liquid resin composition to be obtained by
mixing the hydrolyzed solution of the specified silane coupling
agent and the resol-type phenol resin at a specified ratio, the
friction material which can attain not only the high friction
coefficient but also the excellent compression fatigue property and
the positive gradient of the .mu.-V property can be provided. By
this, trends toward the compactness and light weight of the
friction engaging device in the automatic transmission and, also,
trends toward the high rotation and high output of the automobile
engine can sufficiently be responded. Further, when the friction
material is used in a clutch, a transmission shock can be
prevented.
Still further, according to the invention as set forth in the
second aspect of the present invention, in the hydrolyzed solution
of the silane coupling agent, by allowing an amount of water to be
added to be in a specified range, the non-reacted alkoxy group does
not remain in a large quantity in the hydrolyzed solution,
hardenability is not affected and, then, productivity is not
deteriorated. On the other hand, by arranging such that an excess
amount of water does not remain in a large amount in the hydrolyzed
solution, a content of cured product is allowed to be uniform in a
direction of thickness of the friction material, to thereby
suppress a bad influence on physical strength and a friction
property.
Even still further, according to the invention as set forth in the
third aspect of the present invention, by setting the reaction
molar ratio between any one of the phenols and any one of the
aldehydes to be in a specified range, a remaining amount of
non-reacted phenol monomer is suppressed to be a low level, to
thereby prevent reduction of yield of the resin. Further, by
suppressing unduly increasing of a crosslink density of the phenol
resin, the cured product is prevented from being unduly hard and,
accordingly, the displacement amount of the entire thickness of the
wet friction material is suppressed to be small. Still further, by
setting the number average molecular weight to be in a specified
range, the non-reacted phenol is prevented from being increased
and, also, hardenability is prevented from being reduced. Even
still further, the viscosity of the resin is prevented from being
increased and, also, compatibility of aminosilane to the hydrolyzed
solution is prevented from being reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing comparisons of .mu.-V properties of wet
friction materials in Examples and Comparative Examples at an oil
temperature of 40.degree. C.;
FIG. 2 is a graph showing comparisons of .mu.-V properties of wet
friction materials in Examples and Comparative Examples at an oil
temperature of 100.degree. C.; and
FIG. 3 is a graph showing comparisons of displacement amounts of
entire thickness in Examples and Comparative Examples.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, a wet friction material according to the present invention
will be specifically explained with reference to the preferred
embodiments. In the wet friction material according to the present
invention which contains a paper base material and a binder, a
cured product of a liquid resin composition obtained by mixing a
hydrolyzed solution of a predetermined silane coupling agent and a
resol-type phenol resin is used as a binder. Then, a weight ratio
of respective non-volatile components of the hydrolyzed solution of
the silane coupling agent and the resol-type phenol resin is
adjusted to be in a specified range.
A paper base material used in the present invention is made into
paper in a normal manner from slurry liquid obtained by dispersing,
in water, fiber base materials involving natural pulp fibers such
as wood pulp, organic synthetic fibers such as aramid and inorganic
fibers such as glass, fillers such as diatom earth and a cashew
resin, and a friction regulator. However, the present invention is
not limited thereto.
The hydrolyzed solution of the silane coupling agent as a base of
the binder is prepared by putting a silane coupling agent, water
and, if necessary, a solvent in a reactor and by stirring the
resultant mixture at room temperature or at a relatively low
temperature for a predetermined time. In order to control
hydrolysis of the silane coupling agent and a condensation
reaction, an acid or abase may sometimes be added.
As the silane coupling agent, aminosilane which is excellent in
permeability and adhesiveness to the paper base material and is
represented by the following formula (1) can be used:
(X)(R.sup.1).sub.nSi(OR.sup.2).sub.3-n (1) in which X represents an
alkylamino group containing a primary amine at a terminal; R.sup.1
and R.sup.2 each represents an alkyl group having from 1 to 3
carbon atoms; and n represents an integer of 0 or 1.
Specifically, examples of aminosilane containing three alkoxy
groups in one molecule include 3-aminopropyl trimethoxysilane,
3-aminopropyl triethoxysilane, and N-2-(aminoethyl) 3-aminopropyl
trimethoxysilane. One kind selected from these may be used or a
mixture of two or more kinds selected from these may be used.
Further, examples of aminosilane containing two alkoxy groups in
one molecule include 3-aminopropyl methyl dimethoxysilane,
3-aminopropyl methyl diethoxysilane, N-2-(aminoethyl)
3-aminopropylmethyl dimethoxysilane, and N-2-(aminoethyl)
3-aminopropylmethyl diethoxysilane. One kind selected from these
may be used or a mixture of two or more kinds selected from these
may be used.
The amount of water to be added is not smaller than the amount
permitting hydrolyzing for half the number of alkoxy groups
contained in the aminosilane and also not larger than three times
as much as the amount permitting hydrolyzing for all the number of
hydrolyzable groups. When the amount of water is smaller than the
amount permitting hydrolyzing for half the number of hydrolyzable
groups, a large number of non-reacted alkoxy groups remain in the
hydrolyzed solution so that hardenability is deteriorated. This is
undesirable from the point of view of productivity and energy
saving as well. When the amount of water to be added is contrarily
unduly large, an excessive amount of water remains in the
hydrolyzed solution. As a result, the amount of the hardened
substance becomes uneven in a direction of the thickness of the
friction material so that the unevenness has a bad influence on
physical strength and friction property.
The solvent is not always essentially required but aminosilane in
the starting mixture solution is preferably diluted with a lower
alcohol such as methanol, ethanol, or propanol so that the
aminosilane concentration is not higher than 80% by weight. When
the aminosilane concentration is higher than 80% by weight, a
condensation reaction of silanol groups produced by hydrolysis is
accelerated so that storage stability of the hydrolyzed solution
may be spoiled.
An acid or a base is not always an essential component and is
sometimes used for control the hydrolysis and a condensation
reaction of aminosilane. As for such acids, hydrochloric acid,
sulfuric acid, nitric acid, acetic acid, and hydrofluoric acid are
mentioned. As for such bases, ammonia can be mentioned. However,
the present invention is not particularly limited to those acids
and bases.
In the present invention, the resol-type phenol resin which is
another component of a base of the binder can be obtained by
allowing any one of phenols and any one of aldehydes to react with
each other in the presence of a basic catalyst. On this occasion,
examples of the phenols include phenol, cresol, xylenol, m-cresol,
m-ethyl phenol, resorcin and bisphenol-A, and the present invention
is not particularly limited thereto. These phenols may be used
singly or in combinations. Further, examples of the aldehydes
include paraformaldehyde, formaldehyde, trioxane, acetaldehyde, and
benzaldehyde and the present invention is not particularly limited
thereto. These aldehydes may be used singly or in combinations.
Although a reaction molar ratio (A/P) between any one of the
phenols (P) and any one of the aldehydes (A) is not particularly
limited, the reaction molar ratio is preferably in the range of
from 0.8 to 1.4. When the reaction molar ratio is below the lower
limit of the above-described range, non-reacted phenol monomer may
be increased and, then, yield of the resin is decreased, which is
not preferred; whereas, when the reaction molar ratio exceeds the
upper limit of the above-described range, since the crosslink
density of the phenol resin becomes unduly high, the cured product
becomes harder, with the result that the displacement amount of the
entire thickness of the wet friction material becomes great, which
is not preferred.
Further, a number average molecular weight of the resol-type phenol
resin is not particularly limited, the number average molecular
weight is preferably in the range of from 150 to 400. Note that the
number average molecular weight is a molecular weight calculated in
equivalent in polystyrene by using high-performance liquid
chromatography. When the number average molecular weight of the
phenol resin is below the above-described lower limit, the
non-reacted phenol monomers may be increased and the hardenability
is decreased. On the other hands, the number average molecular
weight excesses the above-described upper limit, viscosity of the
resin may be increased and the compatibility of aminosilane to the
hydrolyzed solution is deteriorated.
Examples of the basic catalysts include alkalis such as sodium
hydroxide, potassium hydroxide, barium hydroxide and calcium
hydroxide, and amines such as ammonia, triethyl amine, and
triethanol amine. These basic catalysts maybe used singly or in
combinations.
Regarding a mixing ratio between the hydrolyzed solution (S) of
aminosilane and the resol-type phenol resin (R), a weight ratio
(S/R) of non-volatile components thereof after subjected to a
heating treatment of one hour at 135.degree. C. is adjusted to be
in the range of from 80/20 to 20/80. When the non-volatile
component of the aminosilane is less than 20% by weight of the
entire non-volatile components, the effect for enhancing the
friction coefficient or the heat resistance may not be achieved,
whereas, when such non-volatile component is more than 80% by
weight, the binder becomes unduly soft to increase the displacement
amount of the entire thickness and the .mu.-V property may
sometimes be in a negative gradient.
A method for mixing the hydrolyzed solution of aminosilane and the
resol-type phenol resin is not limited to a particular manner and,
for example, while stirring a given amount of the resol-type phenol
resin, the hydrolyzed solution of aminosilane is gradually added
thereto, to thereby obtain a uniform mixed solution which has been
mixed with a predetermined amount of the hydrolyzed solution of
aminosilane.
As methods for impregnating the liquid resin composition obtained
by mixing the hydrolyzed solution of aminosilane and the resol-type
phenol resin to the paper base material, for example, there are a
method for dipping the paper base material into the liquid resin
composition, a method for coating the liquid resin composition by
means of any one of various coaters, a method for spraying the
liquid resin composition by means of a spray and the like. Among
these methods, the method for dipping the paper base material into
the liquid resin composition is preferred. With this method, the
impregnating ability of the resin for friction material with
respect to the paper base material can be enhanced.
After the liquid resin composition is impregnated into the paper
base material, the paper base material is ordinarily dried, for
example, by heating at from 80 to 120.degree. C. for 5 to 30
minutes and, then, curing at from 150 to 230.degree. C. for 10 to
50 minutes.
Although a pore ratio of the friction material according to the
present invention is not limited specially, the pore ratio is,
preferably, in the range of from 20% to 70% and, more preferably,
in the range of from 30% to 60%. When the pore ratio is below the
lower limit of the above-described range, a sucking and exhausting
efficiency of ATF may be reduced to reduce the effect for enhancing
the endurance, whereas, when the pore ratio exceeds the upper limit
of the above-described range, the strength of the friction material
may be reduced.
As mentioned above, according to the present invention, in order to
achieve the high friction coefficient and enhancement of the heat
resistance and the positive gradient of the .mu.-V property
requested in the wet friction material, the binder is the cured
product of the liquid resin composition obtained by mixing the
hydrolyzed solution of aminosilane and the resol-type phenol resin
and the weight ratio (S/R) between respective non-volatile
components of the hydrolyzed solution (S) of the silane coupling
agent and the resol-type phenol resin (R) is adjusted to be in the
range of from 80/20 to 20/80.
In the wet friction material according to the present invention, by
using the binder produced by mixing the hydrolyzed solution of
aminosilane which is excellent in permeability and adhesiveness to
the paper base material, soft and excellent in heat resistance and
the phenol resin which is excellent in compression fatigue property
at a specified range, high friction coefficient and a positive
gradient property of the .mu.-V property can be secured without
impairing the compression fatigue property of the friction
material.
EXAMPLES
Now, embodiments of the present invention and comparative examples
will specifically be described in detail with reference to the
accompanying drawings. Incidentally, the embodiments are given to
illustrate the present invention and should not be interpreted as
limiting it in any way. Unless stated otherwise, the terms "part"
and "%" in this specification all indicate "part by weight" and "%
by weight", respectively.
Manufacture of Paper Base Material
A mixture containing cellulose fibers of 35% and aramid fibers of
20% as fiber base components and diatom earth of 45% as fillers is
dispersed in water to obtain a slurry liquid, and a paper is made
from the slurry liquid and is dried to manufacture a paper base
material used in the present invention.
Manufacture of Hydrolyzed Solution of Aminosilane
For Examples 1 to 3 and Comparative Examples 1 to 3 as will
hereinafter be described in detail, the hydrolyzed solution of
aminosilane is obtained as following.
A flask equipped with a stirrer, a reflux condenser, and a
thermometer was charged with 1253 parts of 3-aminopropyl
trimethoxysilane (KBM903: trade name; manufactured by Shin-Etsu
Chemical Co., Ltd.) and, then, diluted with 455 parts of methanol,
added in drops with 378 parts of purified water and allowed to
react for 5 hours at 40.degree. C., to thereby obtain a hydrolyzed
solution of 3-aminopropyl trimethoxysilane. A content of
non-volatile components of the resulting solution after a heat
treatment for one hour at 135.degree. C. was 40%.
Manufacture of Hydrolyzed Solution of Alkoxysilane
For Comparative Example 5 as will hereinafter be described in
detail, the hydrolyzed solution of alkoxysilane is obtained as
following.
A flask equipped with a stirrer, a reflux condenser, and a
thermometer was charged with 1260 parts of lower condensate of
tetramethoxysilane (methyl silicate 51: trade name; manufactured by
Colcoat Co., Ltd.), 858 parts of methanol, 20 parts of 1N
hydrochloric acid and 126 parts of purified water, in dropping
manners and, then, allowed to react for 3 hours at 40.degree. C.,
to thereby obtain a hydrolyzed solution of lower condensate of
tetramethoxysilane. A content of non-volatile components of the
resulting solution after a heat treatment for one hour at
135.degree. C. was 40%.
Manufacture of Resol-type Phenol Resin
A flask equipped with a stirrer, a reflux condenser, and a
thermometer was charged with 1000 parts of phenol and 1050 parts of
37% formalin, and 10 parts of 20% sodium hydroxide and, then,
allowed to react for 1 hours at 100.degree. C. and, thereafter,
dehydrated under a reduced pressure of about 870 hPa (650 mmHg)
and, when a temperature of the resultant solution reaches
70.degree. C., the solution was added with 750 parts of methanol,
to thereby obtain a liquid resol-type phenol resin having a number
average molecular weight of 260. A content of non-volatile
components of the resulting solution after a heat treatment for one
hour at 135.degree. C. was 50%.
Manufacture of Liquid Resin Composition
The thus obtained hydrolyzed solution (content of non-volatile
component: 40%) of aminosilane and resol-type phenol resin (content
of non-volatile component: 50%) are mixed with each other, to
thereby manufacture various types of liquid resin compositions (A
to E) as shown in Table 1.
TABLE-US-00001 TABLE 1 Mixing ratios of types of liquid resin
compositions Hydrolyzed Resol-type solution of phenol Mixing
aminosilane (S) resin (R) ratio.sup.(*.sup.) (S/R) Liquid resin
composition A 100 parts 20 parts 4/1 Liquid resin composition B 100
parts 80 parts 1/1 Liquid resin composition C 40 parts 100 parts
8/25 Liquid resin composition D 100 parts 10 parts 8/1 Liquid resin
composition E 10 parts 100 parts 2/25 .sup.(*.sup.)weight ratio of
non-volatile components
Example 1
The above-described liquid resin composition A was diluted by
methanol and the resulting liquid was impregnated into the paper
base material and then, the impregnated paper base material was
dried and, subsequently, cured by heating it at a temperature of
150.degree. C. for 30 minutes. In this way, a wet friction material
having the paper base material of 100 parts and the binder of 40
parts was obtained. Then, the friction material was punched to
obtain a ring having an outer diameter of 130 mm and an inner
diameter of 100 mm, and the ring was held in a mold, which is
heated to a temperature of 200.degree. C., at pressure greater than
4.9 MPa for 30 seconds to integrate it with a ring-shaped core
plate, to thereby obtain a friction plate having a diameter of 130
mm and a thickness of 2.3 mm.
Example 2
A friction plate having a diameter of 130 mm and a thickness of 2.3
mm was obtained in a same manner as in Example 1 except that the
above-described liquid resin composition B was used as the binder
for the wet friction material.
Example 3
A friction plate having a diameter of 130 mm and a thickness of 2.3
mm was obtained in a same manner as in Example 1 except that the
above-described liquid resin composition C was used as the binder
for the wet friction material.
Comparative Example 1
A friction plate having a diameter of 130 mm and a thickness of 2.3
mm was obtained in a same manner as in Example 1 except that the
above-described liquid resin composition D was used as the binder
for the wet friction material.
Comparative Example 2
A friction plate having a diameter of 130 mm and a thickness of 2.3
mm was obtained in a same manner as in Example 1 except that the
above-described liquid resin composition E was used as the binder
for the wet friction material.
Comparative Example 3
A friction plate having a diameter of 130 mm and a thickness of 2.3
mm was obtained in a same manner as in Example 1 except that the
hydrolyzed solution of aminosilane was used singly as the binder
for the wet friction material.
Comparative Example 4
A friction plate having a diameter of 130 mm and a thickness of 2.3
mm was obtained in a same manner as in Example 1 except that the
resol-type phenol resin was used singly as the binder for the wet
friction material.
Comparative Example 5
A friction plate having a diameter of 130 mm and a thickness of 2.3
mm was obtained in a same manner as in Example 1 except that the
liquid resin composition obtained by mixing 100 parts of the
hydrolyzed solution of alkoxysilane and 80 parts of the resol-type
phenol resin was used singly as the binder for the wet friction
material.
.mu.-V Property
Evaluations as described below were carried out on the friction
plates obtained in Examples 1 to 3 and Comparative Examples 1 to 5
by using a friction performance testing machine (SAE No. 2).
Evaluation methods and results are shown below.
The .mu.-V property was evaluated under the testing conditions
described in Table 2. Results are shown in FIGS. 1 and 2.
TABLE-US-00002 TABLE 2 .mu.-V property testing condition Testing
item Test condition Revolution (rpm) 0.72, 2, 5, 10, 25, 50, 75,
100 Surface pressure 785 kPa Inertia 0.343 N m s.sup.2 Number of
friction face 6 faces Oil amount Oil bath 700 ml Oil temperature
40.degree. C. (FIG. 1), 100.degree. C. (FIG. 2)
As can be seen from FIGS. 1 and 2, in the wet friction materials in
Examples 1 to 3 and Comparative Example 5, in comparison with the
wet friction material in Comparative Example 4 in which a
conventional phenol resin was used as a binder, .mu. (friction
coefficient) is high and is not so much reduced under a high
temperature and, accordingly, temperature dependency of the
friction coefficient is small. Further, the wet friction materials
of Examples 1 to 3 and Comparative Example 5 is excellent in
positive gradient of .mu.-V property; that is, an increasing amount
of .mu. is increased as a speed is increased. In Comparative
Example 3 in which the hydrolyzed solution of aminosilane was used
singly as the binder, .mu. is high in a same was as in Examples 1
to 3; however, when the .mu.-V property exceeds a given speed range
(about 25 rpm), it takes a negative gradient. Although the wet
friction material in Comparative Example 1 uses the hydrolyzed
solution of aminosilane and the liquid resin composition of the
resol-type phenol resin as the binder, since a mixing ratio of the
resol-type phenol resin is small, it behaves in a same manner as in
Comparative Example 1,that is, although .mu. is high, when the
.mu.-V property exceeds a given speed range (about 25 rpm) , it
takes a negative gradient. Although the wet friction material in
Comparative Example 2 uses the hydrolyzed solution of aminosilane
and the liquid resin composition of the resol-type phenol resin as
the binder, since a mixing ratio of the hydrolyzed solution of
aminosilane is small, .mu. is low.
Compression fatigue property
The compression fatigue property was evaluated under the testing
conditions described in Table 3. Further, relative merits of the
compression fatigue property were evaluated in accordance with
dimensions of the displacement amounts of the entire thickness
before and after the tests. Results are shown in FIG. 3.
TABLE-US-00003 TABLE 3 Compression fatigue property testing
condition Testing item Test condition Revolution (rpm) 3600 Surface
pressure 1570 kPa Inertia 0.343 N m s.sup.2 Number of friction face
6 faces Oil amount Oil bath 700 ml Oil temperature 100.degree. C.
Number of cycle 5000 cycles
As can be seen from FIG. 3, in the wet friction materials in
Examples 1 to 3, each displacement amount of entire thickness is
small in a same manner as in the wet friction material in
Comparative Example 4 in which a conventional phenol resin was used
as the binder and is excellent in the compression fatigue property,
in comparison with the wet friction material in Comparative Example
3 in which the hydrolyzed solution of aminosilane was used singly
as the binder and that in Comparative Example 5 in which the
hydrolyzed solution of alkoxysilane and the liquid resin
composition of the resol-type phenol resin were used as the binder.
In the wet friction material in Comparative Example 1, although the
hydrolyzed solution of aminosilane and the liquid resin composition
of the resol-type phenol resin were used as the binder, since the
mixing ratio of the resol-type phenol resin is small, the
displacement amount of the entire thickness is great and, then, the
compression fatigue property was inferior.
While there has been described in connection with the preferred
embodiments of the present invention, it will be obvious to those
skilled in the art that various changes and modification may be
made therein without departing from the present invention, and it
is aimed, therefore, to cover in the appended claim all such
changes and modifications as fall within the true spirit and scope
of the present invention.
* * * * *